the first releases of these in May 2008 were in super short supply,due to 2 factors:

1) short-ordering. most retailers,and even Mattel, thought the 5" line would be the popular one, so MM had a small,limited production run.

2) The Recall. by mid-May Toys R Us, for reasons still speculated on to this day, did an internal recall of the MM figures. once word got out about this, other retailers did a recall too,and these things simply were NOT on pegs anywhere.

now,they started hitting again in July with Series 2 and some stores getting in Series 1 again. the notable difference this time was that the bubbles now had "airholes" running down the sides of them. the initial release figures in May 2008 DID NOT have these holes. which lead to speculation the recall was cause of toxic paint fumes building up in the package,but no one knows for sure. the Joker in Series 2 ( he was rereleased due to popularity) and subsequent releases after this had a different,less detailed paint application around the shirt collar. Batman, however, initially was again in the same standing up pose when Series 1 came back out again. however by late summer/early fall the new pose version - the "kicking" version - started to trickle out. no explanation was ever really given as to why. it just showed up. it also had another difference,in that the original Series 1 Batman's had a dull,matte black costume look. theses new ones had gloss paint on them. same with the Unmasked Chase figures, initial Series 1 release flat black, new Series 1 kicking pose release gloss black.